Yes, you're entitled to use either 32- or 64-bit with any Windows 7 license, even if your OEM doesn't support the other bit-version. This is enforced by MS which is why it's a good thing to change to their activation servers as it does when you use the Product key on COA sticker.
You can use the installer you purchased with the Product Key on Toshiba COA sticker as long as it's the same version, or use the latest official installer linked in
Clean Reinstall - Factory OEM Windows 7.
I'd make your Toshiba Recovery Disks first to have a path back to Factory condition, or save a Windows 7 backup image externally first so that you can go completely clean: Boot the installer, use Custom Drive Options to delete all partitions, create new as you wish or just click Next after deleting all and installer will create and format the install partition for you and begin the install.